1. Field of the Invention
This invention relates to a liquid sealed type vibration isolator used to support a vibration generating member including mainly an automobile engine.
2. Description of the Related Art
The known liquid sealed type vibration isolators, such as an engine mount for supporting a vibration generating member, such as an automobile engine so that the vibration of the vibration generating member is not transmitted to a body include, for example, a liquid sealed type vibration isolator shown in FIG. 26, or a liquid sealed type vibration isolator shown in FIG. 27 or 28.
All of these related art liquid sealed type vibration isolators 100 include a metal fixing member 102 to be secured to one of vibration generating member, such as an engine and a support member, such as a body, a metal fixing member 103 to be secured to the other thereof, a vibration isolating base member 104 connecting these two metal fixing members 102, 103 together and formed of an elastic body of a rubber-like material, a diaphragm 106 provided on the side of the metal fixing member 103 so as to be opposed to the vibration isolating base member 104, a liquid chamber 105 formed between the vibration isolating base member 104 and diaphragm 106, and a partition 107 dividing the liquid chamber 105 into two, i.e. a main liquid chamber 105a and an auxiliary liquid chamber 105b, an orifice 118 communicating the main and auxiliary liquid chambers with each other being formed on an outer circumferential side of the partition 107 to fulfil a vibration damping function of the vibration isolator by an effect of flows of a liquid, which occur owing to the provision of the orifice 118, in the two liquid chambers, and also a vibration insulating function of the vibration isolator by the vibration isolating base member 104.
In the case of the liquid sealed type vibration isolator shown in FIG. 27 or 28, an elastic film of a rubber-like material 180 is provided in addition to the above-described structure, in a central region of the partition 107 by a vulcanization bonding device or a sandwiching device so as to reduce a dynamic spring constant of a high-frequency region (especially, an engine noise region).
In order to obtain stable product characteristics of such a liquid sealed type vibration isolator, it becomes an important factor that the volume, especially, a cross-sectional area of the orifice having a vibration damping function be set to a desired level.
However, all of the liquid sealed type vibration isolators of FIGS. 26, 27 and 28 employ a mode in which an outer circumferential portion of the partition 107 constitutes upper and inner circumferential surfaces and a bottom surface of the orifice, i.e. three sides of a cross section of the orifice, and in which a cylindrical liquid chamber-forming rubber portion 122, which guides the partition 107 for the press fitting of the same thereinto, and which is on the inner circumferential side of a cylindrical trunk portion 114 of the metal fixing member 103, constitutes the remaining one side (outer circumferential surface) of the cross section of the orifice.
Therefore, when, especially, the partition 107 is formed by bending one piece of metal plate by pressure molding or deep drawing, a molding process for forming the three sides of a cross section of the orifice becomes complicated.
When the construction of the partition 107 is simplified so that the pressing or deep drawing thereof can be carried out easily, for the purpose of overcoming the difficulties, there is the possibility that problems arise concerning the radial and vertical positioning of the partition. Especially, when a structure like those of the related art vibration isolators of FIGS. 26, 27 and 28 is employed in which a lower end portion of the partition 107 is bent radially outward with the resultant outer end portion 171 caulked to a caulking portion of the metal fixing member 103, i.e. a fastened section 116 formed by a caulking device and formed of the cylindrical trunk portion 114 and a bottom member 113 of the metal fixing member 103, there is the possibility that the partition 107 slips in the radial and vertical directions due to a tightening force of the caulking device.
When the partition is thus displaced in the radial and vertical directions, the orifice formed by utilizing the partition cannot be set to a desired cross-sectional area, so that stable product characteristics cannot be obtained.
According to an aspect of the present invention, the liquid sealed type vibration isolator is capable of solving these problems, and obtaining stable characteristics.
In the case of the liquid sealed type vibration isolator provided with the elastic film 180 in a central region of the partition 107 which divides the liquid chamber 105 into two, i.e. main and auxiliary chambers, the elastic film setting system has problems different from those encountered in the above-described vibration isolator.
Namely, in the case of the liquid sealed type vibration isolator of FIG. 27, the lower end portion of the partition 107 is caulked to the fastened section 116 of one metal fixing member 103 with an upper end portion of a cylindrical side wall 172 expanded and press fitted into an inner circumference of the liquid chamber-forming rubber portion 122, whereby the orifice 118 is formed between the cylindrical side wall and liquid chamber-forming rubber portion 122. The elastic film of a rubber-like material 180 is vulcanization bonded to a central opening of a top plate portion 123 of the partition 107.
In the case of the liquid sealed type vibration isolator of FIG. 28, the partition 107 is formed of two partition members 107a, 107b. The upper partition member 107a is of a disc type shape, provided with an opening 173 in a central portion thereof and press fitted in the liquid chamber-forming rubber portion 122. The lower partition member 107b is formed to a shape of an inverted cup, bent radially outward at a lower end portion thereof and caulked at the same portion to the fastened section 116 of the metal fixing member 103, provided with an opening 175 in a top plate portion 174 thereof, and has the elastic film of a rubber-like material 180 held between the top plate portion 174 and upper partition member 107a. A space surrounded by an outer circumferential portion of the upper partition member 107a, cylindrical side wall 172 of the lower partition member 107b, and liquid chamber-forming rubber portion 122 forms the orifice 118 which communicates the main and auxiliary liquid chambers 105a, 105b with each other.
Regarding a method of setting the elastic film 180, the partition 107 of the type in which the elastic film 180 is held between two pressing metal members (partition members) shown in the related art example of FIG. 28, the shapes of the two partition members are simplified but two metal press dies for the manufacturing of the partition members become necessary. In the case of the partition in the related art example of FIG. 27 of the type which is formed by bending one piece of metal plate, and vulcanization bonding the elastic film 180 to the bent plate, the molding of the partition itself becomes complicated, and a bonding agent application step has to be carried out before the elastic film has been formed. In all of these cases, the cost increases.
According to another aspect of the present invention, the liquid sealed type vibration isolator capable of solving the above-mentioned problems, facilitating the manufacturing of the partition provided with an elastic film thereon, and reducing the manufacturing cost.
In order to achieve the first-mentioned vibration isolator, the inventors of the present invention earnestly discussed the members by which the orifice should be formed and how to position these members for obtaining a desired cross-sectional area of the orifice, with the simplification of the partition taken into consideration as a premise.
As a result, the inventors discovered that, when the orifice was formed by defining two or one side of across section thereof out of three sides thereof by the partition, and the remaining sides thereof by, for example, the liquid chamber-forming rubber portion, vibration isolating base member or an outer circumferential reinforcing metal member of the diaphragm, and not by defining the three sides of such a cross section by the partition as in the related art examples, the shape of the partition was simplified correspondingly.
Namely, the first-mentioned invention is a liquid sealed type vibration isolator the construction of which is basically identical with those of the above-described related art examples, i.e., includes two metal fixing members for a vibration generating member and a support member, a vibration isolating base member interposed between the two metal fixing members and formed of an elastic body of a rubber-like material, a diaphragm provided so as to be opposed to the vibration isolating base member, a liquid chamber formed between the vibration isolating base member and diaphragm, and a partition dividing the liquid chamber into two, i.e. a main liquid chamber and an auxiliary liquid chamber, an orifice being formed between the partition and a liquid chamber-forming rubber portion on an outer circumferential side thereof, an outer circumferential portion of the partition being formed so as to define at least a part of one or two sides of a cross section of the orifice, either one of the partition and the other orifice-forming member being press fitted or inserted or engaged at a part thereof in a connecting section between the partition and the remaining orifice-forming member into or with the other thereof, whereby the partition and the other orifice-forming member are positioned.
According to this liquid sealed vibration isolator, the partition forms at least only a part of one or two of the wall surfaces of the orifice, the shape of the partition is simplified and variation of the shape thereof decreases. Moreover, the partition and the other orifice-forming member are positioned at the connecting section therebetween by a press fitting or inserting or engaging structure. Therefore, even when a flange portion at a lower section of the partition is caulked to the relative metal fixing member, the partition is retained without being displaced. This enables the partition molding work to be carried out easily, a highly accurate desired cross section of the orifice to be obtained, and stable characteristics to be secured.
In this structure, the partition defines at least a part of two or one side of the cross section of the orifice, so that the positioning of the partition in the liquid chamber becomes an important factor. Therefore, it is specially preferable in view of the accuracy of this positioning operation that a positioning device be formed by providing an annular positioning groove in either one of the partition and the other orifice-forming member, and a free end portion, which is to be press fitted or inserted into the groove, on the other thereof.
In this liquid sealed type vibration isolator, it is possible that the outer circumferential portion of the partition has a mode in which this outer circumferential portion is bent to an L-shaped cross section so as to define the inner circumferential surface and bottom surface of the orifice, and a mode in which the mentioned outer circumferential portion is formed as a substantially vertical wall so as to define the inner circumferential surface of the orifice with the outer circumferential reinforcing metal member of the diaphragm, which is positioned on the lower side of the vertical wall, utilized as a bottom wall of the orifice. All of these modes enable the shape of the partition to be simplified, and variation of the shape thereof and that of the shape of the outer circumferential reinforcing metal member of the diaphragm to be minimized.
A device for positioning the partition of the above-described construction employs the following structure.
When the outer circumferential portion of the partition is formed to an L-shaped cross section so as to define the inner circumferential and bottom surfaces of the orifice, an upper end section of the outer circumferential portion, which defines the inner circumferential surface of the orifice, is extended upward, i.e., in the partition inserting direction, and an annular positioning groove is formed in the liquid chamber-forming edge portion, which is opposed to this upwardly extended portion, of the vibration isolating base member, the partition being positioned by press fitting or inserting the upwardly extended portion into the groove.
Owing to this arrangement, the upper end portion of the partition is engaged with the liquid chamber-side circumferential portion of the vibration isolating base member by the press fitting of the former into the groove of the latter. Therefore, even when a lower portion of the partition is bent and extended radially outward so as to form a bottom wall of the orifice with an outer circumferential end section of the resultant lower extended portion caulked to the relative metal fixing member, the radial and vertical positioning accuracy can be kept high, and a desired cross section of the orifice can be obtained.
Even in the case where the outer circumferential portion of the partition is formed as a substantially vertical wall with the outer circumferential metal member of the diaphragm defining a bottom surface of the orifice, the upper end section of the outer circumferential portion of the partition is extended upward, and an annular positioning groove is formed in the liquid chamber-side circumferential edge portion, which is opposed to this upwardly extended portion, of the vibration isolating base member in the same manner as in the above-described case, the partition being positioned by press fitting or inserting the upwardly extended portion into the groove.
In this case, the partition is also positioned by engaging the upper end portion thereof with the liquid chamber-side circumferential edge portion of the vibration isolating member by press fitting the former into the groove of the latter, while the bottom surface of the orifice is positioned by caulking the outer circumferential reinforcing metal member of the diaphragm to the relative metal fixing member. Accordingly, a desired cross section of the orifice can be retained with a high accuracy.
When the outer circumferential reinforcing metal member of the diaphragm defines the bottom surface of the orifice as mentioned above, it is preferable that the connecting surfaces of the bottom wall of the orifice and the lower end of the partition be sealed, with a rubber member interposed therebetween. When a structure in which an annular groove is formed in this rubber member between the two connecting surfaces with the lower end portion of the partition press fitted or inserted in the groove is employed, the positioning of the two parts can also be done excellently.
The liquid sealed type vibration isolator according to the present invention can also employ a mode in which the lower surface of the outer circumferential portion of the partition constitutes the upper surface of the orifice, the outer circumferential reinforcing metal member, which is positioned on the lower side of the same lower surface, of the diaphragm being formed to an L-shaped cross section so as to define the inner circumferential and bottom surfaces of the orifice, the upper end portion of the reinforcing metal member being brought into pressure contact with the lower surface of the partition via a seal rubber member, whereby this arrangement is utilized for the formation of the orifice. In this case, the simplification of the shape of the partition, facilitation of the molding process and minimization of the variation of the shape of the partition are also attained.
When this structure is employed, it is recommended to bend the outer circumferential end portion of the partition in the upward direction, bring the resultant outer circumferential wall into pressure contact with the inner circumferential surface of the cylindrical liquid chamber-forming rubber portion, and engage the upper end portion of the partition with a flat portion formed on the liquid chamber-side circumferential edge portion, which is positioned above the liquid chamber-forming rubber portion, of the vibration isolating base member, whereby the partition is positioned. This enables the positioning of the partition as well as the outer circumferential metal member of the diaphragm to be done with a high accuracy.
Especially, since the circumferential wall is formed by upwardly bending the outer circumferential end portion the partition, an operation of a rib for heightening the rigidity of the partition is performed thereby. The circumferential wall also plays the role of a guide when the partition is press fitted into the vibration isolating base member along the cylindrical liquid chamber-forming rubber portion.
The partition can also be positioned by bringing the circumferential wall thereof into pressure contact with the inner circumferential surface of the liquid chamber-forming rubber portion, and press fitting or inserting the upper end section of the circumferential wall of the partition into the annular positioning groove formed in the liquid chamber-side edge portion of the vibration isolating base member. This enables the above-mentioned positioning operation to be carried out in a more desirable manner.
The liquid sealed type vibration isolator according to the present invention can also be constructed by forming the outer circumferential portion of the partition as a substantially vertical wall defining an upper half of the inner circumferential surface of the orifice, bending the outer circumferential reinforcing metal member of the diaphragm to an L-shaped cross section so as to define the bottom surface and a lower half of the inner circumferential surface of the orifice, and elastically engaging the upper end of the reinforcing metal member with the lower surface of the partition via the seal rubber member. In this case, the simplification of the shape of the partition, facilitation of the molding process and minimization of the variation of the shape of the partition are also attained.
When a structure is employed which is obtained by extending the outer circumferential end portion of the partition in the upward direction, forming an annular positioning groove in the liquid chamber-side edge portion, which is opposed to the upwardly extended portion, of the vibration isolating base member, and positioning the partition by press fitting or inserting the upwardly extended portion of the partition into the groove, the partition is positioned by the groove provided in the vibration isolating base member as well as the outer circumferential reinforcing metal member of the diaphragm caulked to the relative metal fixing member. When a structure is further employed which is obtained by forming an annular groove in the rubber member, and press fitting or inserting the upper end portion of the reinforcing metal member into the groove, the combining of the partition and the outer circumferential reinforcing metal member of the diaphragm with each other is done excellently, and the positioning accuracy and sealability of these parts are more improved.
In all of the above-mentioned modes, the cross-sectional shape of the orifice formed on the inner side of the outer circumferential surface of the partition is not specially limited but it is preferable, in view of the necessity of simplification of the construction of the partition, that the portion defining the inner circumferential surface of the orifice has a shape close to that of a vertical wall. As long as this condition is satisfied, the orifice may have any of a triangular cross section and a rectangular cross section.
For example, any of a structure in which a cross-sectionally triangular orifice is formed by expanding the lower part of the liquid chamber-forming rubber portion which defines the outer circumferential surface of the orifice, and a structure in which a cross-sectionally rectangular orifice is formed by providing a horizontal flat portion on the part of the liquid chamber-side circumferential edge portion of the vibration isolating base member which is above the liquid chamber-forming rubber portion defining the outer circumferential surface of the orifice, to thereby form the upper surface of the orifice; and having these parts and the partition alone or the outer circumferential metal member of the diaphragm cooperate with each other.
The partition may be obtained by any of the method of molding one piece of metal plate into a bent product, and the method of molding a cast product of aluminum into such a product. Especially, the former method enables the pressing work or deep drawing work to be simplified.
In any of these modes, varying the radial and vertical sizes of the portion to be press fitted of the partition, and the radial and vertical sizes of the groove formed in the vibration isolating base member, into which the partition is to be press fitted,.in such a manner that the groove extends in the direction of the whole circumference of the same base member enable the degree of freedom of a characteristic tuning operation to be increased. Therefore, when the liquid chamber-side circumferential edge portion of the vibration isolating base member is formed as the upper surface of the orifice, a structure is preferably employed which is formed by bending the upper end portion of the relative metal fixing member in the inward direction, and burying the resultant bent portion in the vibration isolating base member to thereby secure an increased rigidity of the portion of the vibration isolating base member which defines the upper surface of the orifice.
The shape of the central region of the partition is not specially limited. For example, when it is necessary in the vibration isolator to reduce a dynamic spring constant in a high-frequency region (especially, an engine noise region), a structure having an elastic film provided in the central region of the partition can also be employed.
In order to achieve the second-mentioned invention, the inventors of the present invention earnestly discussed the. method of setting the elastic film with respect to the partition, to discover that, when one cylindrical partition and an elastic film covering the opening thereof were molded separately with the resultant products positioned firmly, it became possible to reduce the dimensions of a metal vulcanization mold for the elastic film, omit the bonding agent application process, and manufacture the partition at a low cost.
Namely, according to a second aspect of the present invention, the liquid sealed type vibration isolator includes in the same manner as the above-described invention two metal fixing members, a vibration isolating base member interposed between the two metal fixing members and formed of an elastic body of a rubber-like material, a diaphragm disposed so as to be opposed to the vibration isolating base member, a liquid chamber formed between the vibration isolating base member and diaphragm, and a partition dividing the liquid chamber into two, i.e. main and auxiliary liquid chambers, an orifice being formed between the partition and a liquid chamber-forming rubber portion extending around the partition, the partition being formed of one cylindrical partition plate, and a disc type elastic film formed to a diameter larger than that of an opening of an upper cylindrical portion of the partition plate and closing the central opening of the partition plate, the elastic film and partition plate being formed separately, the elastic film being provided with a positioning bore in a lower surface of a circumferential portion thereof, the upper cylindrical portion of the partition plate being press fitted or inserted in the positioning bore.
This structure enables the dimensions of the metal vulcanization mold for the elastic film to be reduced, and the bonding agent application process to be rendered unnecessary. Moreover, the positioning (centering) of the elastic film and partition plate can be done easily.
In order to position the partition vertically, a system for engaging the upper end of the outer circumferential portion of the elastic film with a circumferential wall of the liquid chamber, for example, a liquid chamber-side circumferential edge portion of the vibration isolating base member formed of an elastic body of a rubber-like material; forming a flange portion by bending a lower end portion of the partition in the radially outward direction; and caulking this flange portion to the relative metal fixing member can be employed. Regarding a lower end portion of the partition, a system for supporting a lower end portion of the partition plate by engaging the same lower end portion with the outer circumferential reinforcing metal member of the diaphragm can also be employed.
In all of these cases, an orifice having a desired cross-sectional area can be formed between the partition and the liquid chamber-forming rubber portion on the outer circumferential side thereof, and stable characteristics can be secured.
Concerning the positioning bore formed in the lower surface of the elastic film, the depth thereof is not specially limited. A groove formed in the lower surface of the circumferential portion of the elastic film, or a slit type through hole extending from at least a part of the lower surface of the circumferential portion of the elastic film to an upper surface can also be substituted for the positioning bore. When the through hole is employed, it is recommended that the upper end section, which is press fitted or inserted through the through hole, of the upper cylindrical portion of the partition plate be bent and caulked. This can prevent the elastic film from coming off, and enables the combining of the partition plate with the elastic film to be done reliably. The upper end section of the upper cylindrical portion may be bent either radially inward or radially outward.
The positioning bore is provided preferably so as to extend in the direction of the whole circumference of the elastic film for the purpose of preventing the leakage of a liquid from a clearance between the elastic film and partition plate. In the case of the through hole, forming a connecting portion between the central portion and outer circumferential portion of the elastic film is necessary, so that the through hole has to be formed discontinuously in the circumferential portion thereof.
When the cross-sectional area of the orifice is large, the part of the vertically intermediate portion of the cylindrical partition plate which is lower than the lower surface of the elastic film is expanded to form a stepped section on the same intermediate portion, and this stepped section can be used as a bottom wall of the orifice. This enables an orifice of a desired cross-sectional area to be obtained.
When the positioning bore is formed of a through hole, it is recommended that the upper end portion, which extends through the through hole, of the partition plate be bent radially outward and caulked, and that the elastic film be held in the direction of the height thereof (vertically) between the resultant bent end portion and the stepped section or the lower flange portion of the partition plate. Owing to this arrangement, the fixing of the partition plate and elastic film to each other can be done more easily and reliably.
The elastic film and the upper cylindrical portion of the partition plate which define the inner circumferential surface of the orifice are provided with a first opening communicating the main liquid chamber and orifice with each other, and a second opening communicating the auxiliary liquid chamber and orifice with each other. In order to prevent these two openings from being short-circuited, it is recommended that a partition wall for shutting off an orifice passage be formed on a circumferential portion of the elastic film so as to be integral with the elastic film. Even when this partition wall is provided on any of the vibration isolating base member and the elastic film, the invention can be practiced. However, providing the partition wall on the elastic film is advantageous because it enables the relation between the opening of the orifice passage and partition wall to be determined independently.
The thickness of the elastic film and the diameter of the partition plate are not specially limited but can be selected suitably in accordance with the damping characteristics thereof. Varying the thickness and diameter mentioned above enables a characteristics tuning operation to be carried out easily.